Normal and abnormal response to sperm deposition in female dogs: A review and new hypotheses for endometritis

The reproductive microbiome in dogs: Friend or foe?

The microbiome of the reproductive tract is an area of research in full development. Specifically, the microbiome may be involved in reproductive health, disease, and pregnancy outcomes, as has been shown in humans and animals, including dogs. The aim of the present review was to summarize current knowledge on the microbiome of the canine reproductive tract, to expose the controversial role that some bacterial agents may play in canine subfertility, and to highlight future research perspectives. This review discussed whether the use of antimicrobials in dogs is appropriate to increase reproductive performance and to treat subfertility without proper diagnosis, and the possible use of probiotics to modulate the reproductive canine microbiome. Finally, we indicate areas in which scientific knowledge is currently lacking, and could be promising directions for future research.

Comparing different sperm concentrations for optimizing cooled semen use in the dog

The use of shipping canine semen for artificial insemination has bloomed over the last 20 years. This allows for the spread of genetic material while overcoming geographical or time-related challenges. The optimal sperm concentration for cooled semen transport in the dog is unknown. Often canine semen is extended 1:3-5 vol:vol without standardized sperm concentrations for cooled shipment. We compared different sperm concentrations for cooled storage and hypothesized that lower concentrations would result in better semen quality. Semen was collected from healthy client-owned dogs (n = 8). Individual ejaculates were divided into a control aliquot (CON) extended 1:3 vol:vol with a commercial extender. The remaining sample was centrifuged and extended to 200 ×106 sperm/ml (C200), then serially diluted to 100, 50, and 25 ×106 sperm/ml concentrations (C100-C25). Aliquots were cooled for 24 h and then centrifuged and re-extended. Sperm concentration, plasma membrane integrity (PMI, %), motility (subjective total, STM; computer-assisted sperm analysis (CASA) total and progressive, TM, PM; %), and normal morphology (NM, %) were assessed in raw semen (T0), post-extension (T1), after 24 h of cooling (T2), and after processing at 24 h (T3). Cooling resulted in significant declines in STM and NM for all groups and in decreased PMI for CON and C25-50. After cooling (at T2), PMI was significantly lower for C25 compared with all the groups and higher for CON compared with C25-100 (p ≤ 0.038). Processing and re-extension after cooling further decreased the spermiogram parameters. At T3, PMI for CON was similar to C200 but significantly higher than C25-100, while C25 had the lowest PMI. For motility parameters and NM, C25 performed worse than all or most of the other groups. Comparing CON at T3 with C25-200 at T2, PMI, STM, and NM for CON were significantly lower than C25-200, C200, and C100-200, respectively. In conclusion, our results show that cooling canine semen for 24 h at 200 ×106 sperm/ml final concentration after processing or extending 1:3 vol:vol without centrifugation is preferred based on the highest PMI. If volume restrictions apply, processing raw semen and extending to the desired volume with higher sperm concentrations at the collection facility is superior to centrifugation and volume adjustment after 24 h of cooled storage.

Causes of pregnancy arrest in the canine species

In the canine species, early pregnancy arrest before 30-40 days of pregnancy will induce intra-uterine embryonic or foetal resorption, with very few clinical signs. If no genital examination by ultrasound is performed at that time, it will often remain unnoticed and the bitch will be qualified as infertile. It is only when pregnancy stops at a later stage, mostly after 40 days, that clinical signs will be seen. Expulsion of aborted foetuses or placentas may be observed, although the dam frequently eats the expelled tissues. Intra-uterine mummification may also occur. This article reviews the causes of pregnancy termination in the bitch, both at the embryonic and the foetal stages, reported in the literature. Canine brucellosis is by far the most important disease concerned in this aspect. There is an important current concern about this disease, due to the fact that several outbreaks have been observed recently in Europe, and that it is a very contagious disease; it may be an underestimated zoonosis. Other bacterial causes of pregnancy arrest are sporadic. There is, however, a growing attention towards the microbiological content of raw food diets which are more and more popular among dog breeders and may-if badly prepared-contain abortifacient bacteria such as Campylobacter jejuni or Listeria monocytogenes. The abortifacient role of endogenous vaginal bacteria and mycoplasms remains unclear and may be related to an imbalanced vaginal flora with subsequent ascending bacterial contamination of the uterus. The role of Canine Herpesvirus on abortion is controversial and probably not frequent. Other viruses have been shown experimentally to induce abortion but their natural occurrence in this respect remains unknown. The same applies to the parasite Neospora caninum which is suspected, but not proven, potentially to induce pregnancy arrest in bitches. Among non-infectious causes, uterine pathology such as cystic endometrial hyperplasia (CEH) or sub-clinical post-mating endometritis which can cause infertility and may also induce embryonic resorption. The role of luteal insufficiency in pregnancy arrest is probably overestimated.

General and comparative aspects of endometritis in domestic species: A review

Endometritis is a leading cause of sub- and infertility in domestic animal species. The healthy uterus is colonized by commensal bacteria, viruses and yeast/fungi that represent the nonpathogenic microbiota. A shift in the number or type of organisms accompanied by immune dysfunction, however, may trigger uterine infection and inflammation. Metritis is associated with inflammation of all uterine layers (endometrium, myometrium and perimetrium), whereas endometritis is a more superficial inflammation involving solely the endometrium. Endometritis generally occurs at two time points in domestic animal species, postpartum and postmating. Postpartum endometritis may chronically persist, either as a low-grade disease that often manifests as a vaginal discharge but not a systemic illness (in some species termed clinical endometritis) or sometimes subclinical where features are only detected by endometrial sampling. Contamination of the uterus at the time of mating occurs by direct deposition of semen (ejaculated or artificially inseminated) into the uterus. Improper drainage of the ejaculatory fluid or an inadequate immune response may result in persistent mating-induced endometritis. Both postpartum and postmating endometritis interferes with fertility by creating a suboptimal environment for embryo development and placentation, and chronic endometritis may have an impact on sperm survival and fertilization ability. In the postpartum animal, there may also be changes in milk production and maternal behaviour, which can affect offspring health and survival. Preventive strategies for endometritis largely depend on monitoring their known risk factors, which are sometimes specific with regard to the species. Effective, nonantibiotic therapy for endometritis is not available to date. Overall, extensive research has been performed in cattle and horses to unravel key aspects of endometritis, but in sows and bitches, the available literature is scant. Thus, the need and opportunity to investigate the condition vary considerably among domestic species and necessitate their comparative assessment. This article reviews general and comparative aspects of the diagnosis and classification, pathogenesis, preventive strategies and therapeutics of endometritis in domestic species with a specific focus on cows, mares, sows and bitches.

Progesterone Analysis in Canine Breeding Management

Progesterone is a worthwhile addition to the clinical assessment of cycle stage for breeding, elective cesarian delivery, and reproductive management in the bitch if reliably measured. Clinical decisions based on systemic progesterone concentrations also require the rapid return of results. Most commercially accessible analyses capable of returning results within a day still rely primarily on immunoassays of one kind or another. Point-of-care instruments utilizing similar technology have been developed more recently to enable results to be generated in-house. Repeated monitoring of progesterone on whatever platform can be useful if consistent collection and analysis protocols ensure acceptable precision, accuracy, and repeatability.

Trends in Small Animal Reproduction: A Bibliometric Analysis of the Literature

Simple Summary

Reproduction in small animals is an expanding research area, with focus on breeding improvement and clinical management of domestic carnivores. The aim of the present study was to conduct a bibliometric analysis of the literature of the last decade on small animal reproduction, to point out main sources, most prolific countries, and emerging and neglected topics. Results show that research in biotechnologies for assisted reproduction has a central and increasing role in this field. Diversity in author keywords was also pointed out and a consensus to better categorize research in this field is proposed to reduce this problem in the future.

Abstract

Small animal reproduction (SAR) is a main research field in veterinary medicine and bibliometric analyses are useful to investigate trends in specific research areas. The objective of the present study was to conduct a bibliometric analysis of the literature of the last decade on SAR. A search equation was created, and documents were retrieved from the Web of Science database. Documents were manually revised, categorized and R software version 4.1.2 with Bibliometrix R package version 3.1 and MS Excel were used to perform the analyses. The included documents (n = 1470) were mainly research articles (78%). The top countries for the number of documents and citations were Brazil, United States, Italy, Poland, and Korea. These also account for the most prolific authors and institutions. Analyses by author keywords, categories, and recent reviews of the literature suggest that research on the canine species is more abundant than research on the feline one and that reproductive biotechnologies are a main research focus. Some clinical topics are still considered niche or neglected themes (e.g., semen collection in tomcats, neonatology). However, heterogeneity and ambiguity in keywords and categories are undeniable. This study offers interesting insights, providing definitions for main keywords in the field of SAR.